This invention relates to a method for producing a product containing boron for use as an alloying agent in the manufacture of iron and steel.
The use and effect of boron as an additive for iron and steel are well documented in the literature of the industry. Small amounts of boron in steel increase hardenability markedly. Boron is used in malleable iron in small amounts (0.0005 to 0.004%) to nucleate temper carbon during annealing. Boron acts as a deoxider in cast iron. Bismuth, a strong carbide stabilizer, is added to iron to prevent gray, or mottled structure in heavy sections. Boron is added in both cases as a graphifizer to off-set the carbide stabilizing effects of bismuth and chromium during the primary graphifizing stage.
Boron is presently added to cupola charges and arc furnaces as boron containing 50% ferrosilicon with boron in the range of 0.05 to 0.10%. Boron containing silvery iron is also used. Ferroboron or nickleboron are added in the ladle to provide the boron alloying agent.
Because the above-described techniques cause the boron content to vary from heat-to-heat due to the variability of the boron containing alloy agent and, because the materials used are expensive, it is desirable to develop a method for producing a boron containing product for use as an alloying agent which is both inexpensive and simple to produce. Further, it is desirable to produce a product which can be easily handled by the automatic weighing and batching equipment used in the iron and steel industry. This invention accomplishes these objectives by a method heretofore believed unadaptable for use with boron compounds, that of adding boron to cement bonded agglomerates.
The problem associated with the addition of boron containing compounds to cement bonded materials, such as concrete or ferroalloy agglomerates, has been the characteristic retardation of the setting time of the flowable cement mixture. In massive concrete placements, such as large dams, the retardation of setting time is desirable to allow placement and consolidation without cold joints or to prevent excess heat buildup. Likewise, retardation may be desirable in hot weather. However, for the preparation of cement bonded ferroalloy agglomerates, economics dictate rapid setting or curing of the materials to produce the maximum quality of agglomerate in the shortest period of time. This invention overcomes the retardation of setting time by a simple, inexpensive method.
The above and other objects and features of this invention will become apparent from the following specification, detailed description and appended claims.